Numerical investigation of the application of high temperature air combustion in an industrial furnace

Abstract

Numerical simulation of turbulent combustion in the radiation section of an industrial steam cracking furnace is carried out in classical premixed and newly developed high temperature air combustion (HiTAC) regimes. The eddy dissipation concept coupled with the detailed KEE-58 mechanism is employed to resolve turbulence–chemistry interaction and combustion chemistry. Three simulations with highly preheated atmospheric air (19%wt oxygen) and diluted fuel are performed to study the attractive features of the so-called HiTAC regime. It is shown that when the inlet air temperature increases to 1100 K, fuel dilution can provide favorable characteristics of the high temperature air combustion. In this temperature, combustion continues even under extremely fuel-lean conditions such as 1.5%wt of methane in the reactants. Calculation of the Damköhler number determined that a finite-rate reaction zone is volumetrically extended throughout the furnace. Computation of NO x emission from different chemical routes revealed that 80% reduction of NO x formation in fuel-diluted high temperature air combustion regimes could be achieved compared to the normal firing condition. Moreover, the results implied that the emission of NO x in normal firing and high temperature air combustion conditions was mainly attributed to thermal/prompt and prompt/NNH mechanisms, respectively.